Sea surface pCO2 variability and air-sea CO2 exchange in the coastal Sudanese Red Sea

Type Article
Date 2021-05
Language English
Author(s) Ali Elsheikh B.1, Skjelvan IngunnORCID2, Omar Abdirahman M.2, Olsen AreORCID3, de Lange Tor E.3, Johannessen Truls3, Elageed SalmaORCID1, 3
Affiliation(s) 1 : Institute of Marine Research, Red Sea University, Port Sudan, Sudan
2 : NORCE Norwegian Research Centre, Bjerknes Centre for Climate Research, Bergen, Norway
3 : Geophysical Institute, University of Bergen and Bjerknes Centre for Climate Research, Bergen, Norway
Source Regional Studies in Marine Science (23524855) (Elsevier BV), 2021-05 , Vol. 44 , P. 101796 (11p.)
DOI 10.1016/j.rsma.2021.101796
Keyword(s) Sea surface pCO2, CO2 flux, time series, coastal Red Sea, seasonality
Abstract

The dynamics of sea surface pCO2 () and air-sea CO2 exchange of the Sudanese coastal Red Sea has for the first time been studied over a full annual cycle (October 2014 - October 2015) based on semi-continuous measurements from moored autonomous sensors. showed a seasonal amplitude of approximately 70 atm, overlaid by a high frequency (3-4 days) signal of around 10 atm. The highest values, of about 440 atm occurred during summer and fall, while the lowest values of about 370 atm occurred during winter. The monthly change was primarily driven by temperature, i.e., heating and cooling of the water surface. Additionally, Dissolved Inorganic Carbon (DIC) and Total Alkalinity (AT) contributed significantly to the observed change in as a consequence of along-coast advection and upwelling of CO2-rich deep water, and likely biological production, and uptake of atmospheric CO2. The area is a net annual source for atmospheric CO2 of 0.180 0.009 mol CO2 m−2 y−1. Based on a compilation of historic and our new data, altogether covering the years 1977 to 2015, long term trends of were determined for the seasons winter-spring (1.75 0.72 atm y−1) and summer -fall (180 0.41 atm y−1), both weaker than the atmospheric trend (1.96 0.02 atm y−1). We are suggesting that the study region has transformed from being a source of CO2 to the atmosphere throughout the year to becoming a sink of CO2 during parts of the year. The long term trend was to a large degree driven by increasing DIC, but increasing AT and temperature also played a role.

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